Heat conducting seal

ABSTRACT

A mechanical face seal, for sealing about a rotating shaft, includes a seal head assembly in sealing engagement with a seal seat assembly. The seal seat assembly has a washer with a portion that is sandwiched between a grommet and a seal seat. Another portion of the washer is sandwiched between a sleeve or shoulder on the shaft and an impeller. Frictional heat generated by the seal can be conducted away from the seal seat to the sleeve or shoulder on the shaft, which is particularly advantageous when the face seal is operated without water adjacent to the seal seat.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/441,371, filed on Jan. 20, 2003. The disclosure of the aboveapplication is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates in general to shaft seals, and moreparticularly to mechanical face seals employed with rotating shafts.

BACKGROUND OF THE INVENTION

A mechanical face seal, which may be employed for example in adishwasher, may include a stationary seal head assembly that mates withand seals against a rotating seal seat assembly. Typically, the sealseat assembly mounts to an impeller that is driven, via a shaft, by apump. It is common for the impeller to be made of a plastic material.Such a conventional face seal assembly performs very well at sealing outwater, and prevents the impeller from overheating because the wateradjacent to the seal absorbs frictional heat generated by the seal. Aconcern arises, however, with these conventional face seals, when thepump is run dry—that is, the pump is run, but a water supply valve isclosed, thus preventing water from flowing adjacent to the face seal forcooling the seal. This situation can happen, for example, in adishwasher, when a dishwasher is installed, but the water supply valveis not opened. If the dishwasher is then run, there is no water adjacentthe seal to carry away the frictional heat generated by the sealoperation. The frictional heat then builds up, and some of the heat willtransfer into the impeller, which also will have no water surrounding itto carry away heat. After operating in this way for a relatively shorttime, the heat in the impeller can build up to the point where it willpartially melt and possibly decouple from an impeller hub. This candestroy the impeller pumping ability and possibly create a water leakpath.

Thus, it is desirable to have a face seal for a rotating shaft that willadequately seal water, and can also significantly reduce the chance ofheat build up damaging a mating component, such as an impeller, even ifthe face seal is run in a dry environment.

SUMMARY OF THE INVENTION

In its embodiments, the present invention contemplates a heat conductingseal seat assembly The seal seat assembly includes a seal seat adaptedto be in surface contact with a seal head assembly, a grommet, and aheat conducting washer having a first portion located between the sealseat and the grommet, and a second portion abutting a heat sink.

An advantage of the present invention is that a seal seat assembly candissipate frictional heat generated during dry pump operation, thussignificantly reducing the chance of impeller and/or pump failure. In adishwashing machine, for example, if the dishwasher is run without thewater supply valve open, then one will have dry pump operation. The sealseat assembly dissipates extra generated heat, thus significantlyreducing the chances of seal damage that can lead to pump failure andlater water leakage.

Another advantage of the present invention is that a washer mountedadjacent a motor shaft sleeve or shoulder will allow the impeller to beaugered onto the shaft while preventing it from being augered on toofar. This significantly reduces the chances of a seal failure due toaugering of the impeller too far onto the shaft.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

The drawing is a cross-sectional view of a seal assembly in accordancewith the principles of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

The drawing illustrates a mechanical face seal assembly 20 mounted abouta rotatable shaft 22. The rotatable shaft 22 may be driven by, forexample, a pump motor 23 in an automatic dishwasher—although, the sealassembly 20 may be employed in other types of sealing applications for arotatable shaft 22. The shaft 22 includes a shaft sleeve 26 mountedthereon. As an alternative to a shaft sleeve, the shaft 22 may have ashoulder formed thereon.

The seal assembly 20 includes a seal head assembly 24, mountedstationary relative to a pump housing 21, and a heat conducting sealseat assembly 28, rotationally fixed to the shaft 22. A bearing 29mounts on the shaft 22, with an inner race thereof abutting the shaftsleeve 26.

The heat conducting seal seat assembly 28 includes a seal seat 30, whichabuts against the seal head assembly 24, a grommet 32, which abuts animpeller 34, and a washer 36, having a first portion 31 captured betweenthe grommet 32 and the seal seat 30. A second portion 33 of the washer36 is also clamped between the impeller 34 and the shaft sleeve 26. Theimpeller 34 is preferably threaded onto the motor shaft 22, which clampsthe washer 36 against the sleeve 26. The washer 36 is preferably made ofmetal, such as aluminum, the cup shaped grommet 32 is preferably made ofan elastomeric material such as rubber, and the impeller 34 ispreferably made of an elastomer and/or plastic. The seal seat 30 ispreferably made of stainless steel, although other suitable face sealmaterial, such as for example ceramic, may be employed if so desired. Aface seal component 38 of the seal head assembly 24 is biased againstthe seal seat 30 via a spring 40. The seal head assembly 24 includes anelastomeric seal member 42 supported by a retainer member 44.

In operation, if the pump motor 23 is operated while the water supplyvalve for the dishwasher is closed, then the seal seat assembly 28 willhelp by conducting away heat. Specifically, the washer 36 conductsfrictional heat from the seal seat 30 to the shaft sleeve 26, whichserves as a heat sink. This provides a direct heat path between the sealseat 30 and the sleeve 26. Moreover, the grommet 32, by encapsulatingthe outside of the seal seat 30 and the washer 36, insulates the heatfrom the impeller 34. This significantly reduces the chances that enoughheat will reach the impeller 34 to cause any damage. If the water supplyvalve for the dishwasher is open, then the water itself will absorb muchof the heat generated at the seal. So again, the impeller 34 isprotected from overheating.

While certain embodiments of the present invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention as defined by the following claims.

The description of the invention is merely exemplary in nature and,thus, variations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A face seal assembly for a rotatable shaft, the face seal assemblycomprising: a seal head assembly adapted to be rotationally fixedrelative to a housing, said seal head assembly including a face sealcomponent attached to an elastomeric seal member and further including aspring biasing said face seal component in an axial direction; a sealseat assembly mounted to said rotatable shaft and including a seal seatin contact with the seal head assembly and a heat conducting washerhaving a first generally flat surface portion disposed between andagainst an axial end face of said seal seat and a grommet, and said heatconducting washer having a second generally flat surface portiondisposed against heat sink means disposed on said shaft for conductingheat away from said seal seat, wherein said axial end face has aradially extending generally flat portion circumscribing said shaft andsaid first portion of said heat conducting washer is in heat conductingcontact with a majority of said seal seat.
 2. The face seal assembly ofclaim 1 wherein said grommet surrounds said first generally flat surfaceportion of said heat conducting washer and said seal seat.
 3. The faceseal assembly of claim 1 wherein said heat sink means includes a sleevedisposed on said shaft.
 4. The face seal assembly of claim 1 whereinsaid heat conducting washer is made of metal.
 5. The face seal assemblyof claim 1, wherein said first and second portions of said heatconducting washer are radially spaced apart.
 6. The face seal assemblyof claim 5, wherein said first and second portions of said heatconducting washer are radially spaced apart such that said first andsecond portions do not overlap one another.
 7. The face seal assembly ofclaim 5, wherein said first portion is spaced radially outwardly fromsaid second portion.
 8. A heat conducting seal seat assembly for arotatable shaft comprising: a seal seat adapted to be in surface contactwith a seal head assembly; a grommet surrounding said seal seat; and aheat conducting washer having a first portion clamped between the sealseat and the grommet and in direct contact with the seal seat andgrommet, and a second portion axially abutting heat sink means disposedon the shaft for conducting heat away from said seal seat.
 9. The heatconducting seal seat assembly of claim 8 wherein said seal seat is madeof stainless steel.
 10. The heat conducting seal seat assembly of claim8 wherein said grommet is made of an elastomeric material.
 11. The heatconducting seal seat assembly of claim 8 wherein said washer is made ofmetal.
 12. The heat conducting seal seat assembly of claim 8 whereinsaid heat sink means is a sleeve adapted to mount about said shaft. 13.The heat conducting seal seat assembly of claim 8, wherein said firstportion of said washer has opposite substantially flat radiallyextending surfaces, said seal seat has a substantially flat radiallyextending surface in direct contact with one of said substantially flatradially extending surfaces of said first portion, and said grommet hasa substantially flat radially extending surface in direct contact withthe other one of said substantially flat radially extending surfaces ofsaid washer.
 14. The heat conducting seal seat assembly of claim 8,wherein said first portion of said heat conducting washer is axiallyoffset from said second portion of said heat conducting washer.
 15. Asealing system comprising: a housing; a motor mounted to said housing; ashaft driven by said motor and rotatably supported by said housing; animpeller mounted to said shaft; a seal head assembly fixed relative tosaid housing and surrounding said shaft, said seal head assemblyincluding a face seal component attached to an elastomeric seal memberand further including a spring biasing said face seal component in anaxial direction; and a seal seat assembly mounted to said rotatableshaft and including a seal seat in contact with said seal head assemblyand a heat conducting washer with a first generally flat portion clampedaxially between a grommet, said seal seat and said impeller, said firstportion directly engaging said seal seat, and a second generally flatportion clamped axially between said impeller and a heat sink meansdisposed on said shaft for conducting heat away from said seal seat,wherein said seal seat is substantially axially stationary relative tosaid shaft and said face seal component can move axially relative tosaid shaft.
 16. The sealing system of claim 15 wherein said grommetsurrounds a portion of said heat conducting washer and said seal seat.17. The sealing system of claim 15 wherein said heat sink means includesa sleeve disposed on said shaft.
 18. The sealing system of claim 15wherein said heat conducting washer is made of metal.
 19. The sealingsystem of claim 15, wherein said first generally flat portion of saidheat conducting washer circumscribes said shaft.
 20. The sealing systemof claim 15, wherein said seal seat has a radially extending generallyflat surface that circumscribes said shaft and said first generally flatportion of said heat conducting washer is in heat conducting contactwith a majority of said radially extending generally flat surface ofsaid seal seat.